Ampicillin-resistant Haemophilus influenzae type B was isolated from four children: two with meningitis, one with septicemia, and one with otitis media. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the isolates, tested by tube dilution assays, were 6.25μg to 50μg/ml and 12.5μg to greater than 50μg/ml, respectively. Epidemiological studies demonstrated a link between the two patients with meningitis and suggest that the infection in the child with septicemia was hospital-associated. These cases emphasize the need for careful sensitivity testing of significant H influenzae isolates. The poor response to ampicillin in at least one of our cases suggests revision in management of severe H influenzae infections according to local experience.
(JAMA 229:295-297, 1974)